Conventionally, there has been known a mobile communication system in which a plurality of radio base stations receive an uplink signal transmitted from a radio terminal coordinated with one another. In such a mobile communication system, selection combining of the uplink signals received in the plurality of radio base stations is performed.
For example, in LTE (Long Term Evolution), the uplink signal is transmitted through PUSCH (Physical Uplink Shared Channel). The transmission power control of the uplink signal is performed on the basis of the path loss between the radio terminal and the radio base station.
However, a case is assumed wherein in a mobile communication system in which a plurality of radio base stations receive an uplink signal transmitted from a radio terminal coordinated with one another, when the transmission power control of the uplink signal is performed on the basis of the path loss between any one radio base station of the plurality of radio base stations and the radio terminal, the transmission power of the uplink signal becomes excessive.
For example, a case is assumed in which a radio base station that manages a pico cell (hereinafter, called a pico base station), and a radio base station that manages a macro cell (hereinafter, called a macro base station) coexist as the radio base station, and the transmission power control of the uplink signal is performed on the basis of the path loss between the macro base station and the radio terminal. In such a case, when the radio terminal is isolated from the macro base station and is positioned near the pico base station, the transmission power of the uplink signal becomes excessive for the pico base station.